1. Field of the Invention
The present invention relates to hybrid multilayer substrates and methods for manufacturing the same, and more particularly, to a highly reliable hybrid multilayer substrate having a cavity in which an electronic component is mounted with high accuracy, and to a method for manufacturing the hybrid multilayer substrate.
2. Description of the Related Art
A related wiring substrate having a cavity is disclosed in Japanese Unexamined Patent Application Publication No. 2003-309213 (Patent Document 1). This wiring substrate includes a ceramic core substrate having a penetrating hole, a resin insulating layer which is provided on the bottom surface of this ceramic core substrate and which blocks the penetrating hole so as to define a cavity, an IC chip mounted in the cavity defined by the resin insulating layer, and a filling material which is filled around the IC chip to seal it in the cavity.
When the above wiring substrate is manufactured, after the ceramic core substrate having a penetrating hole is formed, the IC chip is aligned in the penetrating hole of the ceramic core substrate, and the filling material is then filled in a gap between the IC chip and the penetrating hole so as to unite the IC chip and the ceramic core substrate in the penetrating hole. Next, by a conventional method, a resin insulating layer having via holes is formed on the rear surface of the ceramic core substrate.
However, with the wiring substrate disclosed in Patent Document 1, since the resin insulating layer having via holes is provided for the IC chip fixed in the penetrating hole of the ceramic core substrate by the filling material, and a self-alignment function of the IC chip cannot be used during mounting, terminals of the IC chip and the via holes (electrodes) of the resin insulating layer cannot be easily and accurately provided, and as a result, it is difficult to obtain electrical conduction between the IC chip and the electrodes provided in the resin insulating layer. Furthermore, since IC chips are multifunctional in recent years, in ICs for flip-chip assembly, the pitch between terminals is decreased, the size of bumps is decreased, and the number of pins is increased. As a result, it is increasingly difficult to obtain electrical conduction between the IC chip and the electrodes provided in the resin insulating layer.
In order to use the self-alignment function of the IC chip, it is necessary to form a cavity 3 in advance by thermocompression bonding of a resin insulating layer 2 having electrodes 2A to a ceramic substrate 1 having a penetrating hole as shown in FIG. 11. Furthermore, concomitant with the increase in the number of pins, due to the narrower pitch and smaller bumps of an IC chip, the electrodes 2A must be formed with high accuracy in the cavity 3 so as to reduce the shift in position of the electrodes 2A to as small as possible.
However, as shown in FIG. 11, when the resin insulating layer 2 is bonded to the ceramic substrate 1 by thermocompression bonding, the resin insulating layer 2 flows during the thermocompression bonding, the electrodes 2A located in the cavity 3 are shifted in the horizontal direction thereby, and thus, it is difficult to form the electrodes 2A with high accuracy. This tendency becomes more apparent as the number of films which define the resin insulating layer 2 is increased, and as a result, the reliability of connection may not be satisfactory in some cases.